COPD is a world-wide health problem of increasing prevalence. Non-invasive markers of disease phenotype, severity and rate of progression of the disease, markers characterizing exacerbations of COPD are badly needed. We propose to analyze ultrafiltered exhaled air samples, to establish optimal protocols for sample collection following a FEV1 maneuver, to survey lipids including phospholipids, eicosanoids, steroids, nucleosides, proteins and peptides as markers of potential disease (activity). We propose to establish quantitative mass spectroscopic techniques (using stable isotope dilution protocols) for target marker assays. We propose to investigate stable COPD patients before and during supplemental continuous flow oxygen treatment, before and during alpha-l-antitrypsin infusion therapy, before and after smoking cessation and before and after lung transplantation.